Login into GNOME desktop remotely

To login to your GNOME desktop session, you should use a vnc server to connect to GDM’s X session. It is not possible to do this when GDM uses wayland session.

Setup

You need to install and configure x11vnc. On debian:

# apt-get install x11vnc net-tools
# x11vnc -storepasswd

GDM must be configured to use X11.

/etc/gdm3/daemon.conf:

[daemon]
WaylandEnable=false

Usage

SSH into the box and launch x11vnc as GDM’s user. On debian:

# sudo -u Debian-gdm x11vnc -auth /run/user/$(id -u Debian-gdm)/gdm/Xauthority -display :0 -nopw

Then you can connect to the server from any vnc client and login to your user.
After login, you can relaunch x11vnc as your user to access your desktop:

# sudo -u username x11vnc -auth /run/user/$(id -u username)/gdm/Xauthority -display :1 -nopw